1. Field of the Invention
The invention relates to a hot-blast main for a hot-blast stove system of a blast furnace. The main comprises a brickwork structure of a plurality of courses of refractory bricks forming a conduit for hot gas. Such a hot-blast main is generally known from the practice of blast-furnace plants.
2. Description of the Prior Art
A hot-blast main with a plurality of brick courses is described for example in the French patent specification no. 2193174. The courses of refractory bricks are in this construction on the outward side of an insulating inner lining, and directly adjoin the steel outer shell of the hot-blast main. The courses are composed of, for example, porous alumina bricks of a quality which is chosen in dependence on the temperature level at the position of the insulating lining during operation of the hot-blast stove system.
In the applications of such a hot-blast main at elevated temperatures the refractory inner lining mentioned is usually made of silica. Consequently this has different thermal expansions from the outer courses of refractory bricks. The overall expansion pattern is complex, because the coefficients of thermal expansion of these materials vary with temperature. In practice the construction is provided with an expansion possibility to compensate for these thermal expansion differences. However, the technical problem then to be solved is to design the main in such a way that it is stable both in cold condition, during heating up and in operating condition, since in certain applications the innermost refractory lining comes into contact with hot blast of temperature as high as 1500.degree. C.